Nitride semiconductors such as AlGaN, InGaN, and the like, in which a portion of the group III element is replaced with Al, In, and the like, are used in semiconductor light emitting devices. In the case where a group III source-material gas and a group V source-material gas mix excessively in the apparatus when depositing AlGaN using metal organic chemical vapor deposition, reaction products that do not contribute to the growth on the substrate are produced; limitations on the Al composition occur; and the uniformity in the surface and reproducibility of the composition and film thickness decrease. Therefore, configurations have been employed to introduce the group III and group V source-material gases in a separated state up to the proximity of the substrate. For example, JP-A 11-354456 (Kokai) (1999) discusses technology in which a source-material gas including a group III source and a nitrogen source is introduced substantially parallel to the substrate surface and in a laminar configuration. Further, JP-A 2007-317770 (Kokai) discusses technology in which a through-hole is provided in a terminal portion of a partition of a vapor deposition apparatus to mix the source-material gases to provide a vapor phase reaction under more uniform conditions.
On the other hand, although it is desirable to increase the flow rate ratio of the group V source-material gas when depositing, for example, InGaN, increasing the flow rate ratio in a configuration in which the group III and group V source-material gases are introduced in a separated state up to the proximity of the substrate causes turbulent flow to occur and reduces the uniformity in the surface and the reproducibility. By conventional art, it is difficult to perform deposition with proper conditions for each semiconductor layer having a different composition.